Is CVE-2026-40685 in the CISA KEV catalog?

No. CVE-2026-40685 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40685?

CVE-2026-40685 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2026-40685?

CVE-2026-40685 has an EPSS score of 0.32% (24th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-40685?

Upgrade exim4 on debian 12 to 4.96-15+deb12u9 or later. Fixes are available for 7 affected products.

CVE & CISA-KEV Catalog

CVE-2026-40685

MEDIUM

6.5

CVSS v3

NVD

Description

In Exim before 4.99.2, when JSON lookup is enabled, an out-of-bounds heap write can occur when a JSON operator encounters malformed JSON in an untrusted header, because of an incorrect implementation of \ skipping.

CWE-684 CWE-787Out-of-bounds Write

How to fix

Remediation Available

exim4Debian

Fixed in:4.96-15+deb12u9CVE-2026-40685

Fixed in:4.98.2-1+deb13u2CVE-2026-40685

Fixed in:4.99.2-1CVE-2026-40685

exim4Ubuntu

Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1

Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1

Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1

Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1

Fixed in:4.95-4ubuntu2.7USN-8228-1

Fixed in:4.97-4ubuntu4.4USN-8228-1

Fixed in:4.98.2-1ubuntu2.1USN-8228-1

exim4-baseUbuntu

Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1

Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1

Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1

Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1

Fixed in:4.95-4ubuntu2.7USN-8228-1

Fixed in:4.97-4ubuntu4.4USN-8228-1

Fixed in:4.98.2-1ubuntu2.1USN-8228-1

exim4-daemon-heavyUbuntu

Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1

Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1

Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1

Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1

exim4-daemon-lightUbuntu

Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1

Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1

Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1

Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1

exim4-devUbuntu

Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1

Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1

Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1

Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1

eximon4Ubuntu

Fixed in:4.82-3ubuntu2.4+esm9USN-8382-1

Fixed in:4.86.2-2ubuntu2.6+esm9USN-8382-1

Fixed in:4.90.1-1ubuntu1.10+esm6USN-8382-1

Fixed in:4.93-13ubuntu1.12+esm1USN-8382-1

Fixed in:4.95-4ubuntu2.7USN-8228-1

Fixed in:4.97-4ubuntu4.4USN-8228-1

Fixed in:4.98.2-1ubuntu2.1USN-8228-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

Exploit Intelligence

0.32%probability of exploitation in 30 days

24thpercentile

Low risk: more likely to be exploited than 24% of all known CVEs.

References

Patch1

code.exim.org

Vendor Advisory1

exim.org

Third-Party Advisory1

openwall.com

Other references1

exim.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-01.